Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$149.65	4.774%	$156.7943	$156.79	$156.80	$156.80
Purchase #2	$104.62	11.135%	$116.2694	$116.27	$116.25	$116.30
Purchase #3	$240.76	9.543%	$263.7357	$263.74	$263.75	$263.70
Purchase #4	$55.71	6.624%	$59.4002	$59.40	$59.40	$59.40
Purchase #5	$183.45	7.314%	$196.8675	$196.87	$196.85	$196.90
Purchase #6	$77.55	11.716%	$86.6358	$86.64	$86.65	$86.60
Purchase #7	$235.50	11.820%	$263.3361	$263.34	$263.35	$263.30
7 purchase totals =	$1,047.24		$1,143.0390	$1,143.05	$1,143.05	$1,143.00